Let me begin by saying that I lack the 3.x experience to comment on these mechanically, so I'll be basing this on flavor. That said, I like most of these classes, hence why I'm commenting on them at all.
I really like this one - everything about it says slaughter.
Black Lore Sentinel
I quite like the fluff here, but the powers seem too rogue-like to me. I'd like to see more focus on secrets and intrigue than on Sneak Attacks and darkness.
For example, I think intriguing abilities could include stuff like being able to rip secrets from the minds of the unwilling, or some sort of Litany of Secrets - advancing on the target, revealing his deepest, darkest secrets for all nearby to hear, esentially reducing him into a quivering wreck ("Whuh... What are you?! Get away from me! Get away!).
Just a thought.
Hound of Orcus
After the last one, this one seems a bit... bland. It's sort of just another 'turns wizard into combat guy' kind of class.
This one seems to lack actual divine-ness. Most of the abilities seem personally developed, rather than granted by Gruumsh.
Let me start by saying that I love the picture. On the actual class, while the War part of the portfolio is clearly depicted, I'd like to see a bit more Tyranny. By which I mean that, while I generally dislike the idea of obviously battlefield control abilities in D&D, if anyone should get it, it seems like it should be the chosen of Hextor. I'd like to see him able to exert some sort of loose control over weak-minded enemies, who are basically cowed into obedience by his sheer presence.
It would probably be very brief control, as the enemy quickly realizes that the Battlefiend is a foe, but it could still be useful.
Just my thoughts. I do like most of what's here.